For #2 question, you have to be far enough away from the spawn point for a group to generate. Basically, to be "safe", you would want to be about 40nm away from the spawn location. If you are after torpedo fodder, don't use a regular Group or Unit, but use the Random Generated Group (RGG) instead. Here is a screen shot, zoomed-in on an RGG. Now, you'll not get both of those windows to open together - that is a "double-exposure" for illustration purposes only... tic:
You right-click on the screen where you want the group to "spawn" into the game, and choose the "Add Random Generated Group" menu item. From that, you'll get a naming dialog box, where you name the group. If it's the only one you're going to have, keep it the same. If you're going to add more, then you'll have to change the names since the game can't do duplicates. You can also choose whether it will be an Air Group, Land Group, or Naval Group (the default). After that, the "Define Group Contents" dialog pops up (though there's no name on it). That is the dialog box in the lower right of the pic above. Choose the country and type of ship from the list, and click on the "Add Entry" button (you can also choose how many - "Units No", the spawn probability, and the crew rating setting). If you make a mistake, no big deal, just highlight the unit in the left window, and make a new selection in the right window, then click the left window again, and it will change to the new choice. When you add a DD or similar to the group, there is the tick box choice for "Position as escort" that becomes active, so that it can either patrol out front or the sides, or be a part of the group. When part of the group, the DD for some reason become dumber than a box of rocks. Don't forget to set the "Leader Entry" at the bottom right, since it determines how your group reacts to enemy submarine activity, and also choose how many columns of ships you want. The "Formation spacing" is really important. With the big ships, you will want at least 800 meters between them, else the group will have trouble maintaining "convoy formation", because their "collision avoidance" routine kicks in. When you're finished with adding the vessels (or airplanes, if you chose an Air Group), click on the "Accept" button, and you're back at the full ME screen.
If you select the RGG and then right-click on it, you'll get a menu up. This time, choose "Group Properties", and you'll get that dialog that's toward the left in the pic above. From it, you can choose the group's initial speed, which will be limited by the slowest vessel in the group you built. If you later add or alter vessels in the group, you will want to double-check that "Speed (Max)" value, and be certain your WayPoints don't exceed that, else you'll have issues with the group performing as expected. Anyway, you will want to pay attention to the "Max group instances created", which defaults to 10,000 and the "Max number of units in RGG". If you've only got 6 vessels in the group, set that number to "6", naturally. If you're going to shoot at say six groups, but it might take a bit to get to the location where you ambush is to take place, allow for that and limit the number of groups that generate. However, neither of these are absolutely necessary with what you're doing, and could be left at their default values.
The "Entry Date" and "Time", and the "Exit Date" and "Time" are somewhat important. You don't want to miss the action, nor get there before it starts. Your "Human controlled" submarine has to enter the scenario on the same date that the mis file is built for, but the other assets are not restricted to that, so if you don't find what you expect, be sure and check these dates / times.
The part you are most interested in, and why you would want to use an RGG instead of a regular group or unit, is because of the "Repeat interval (hours)", and the "Group spawn probability (%)" boxes. The default for Repeat interval is 24 (hours), so once a day. You can set that to "1" hour if so desired. However, be certain to give yourself enough time between attacks to get re-set. The "percentage" can be from 0% (never spawns) to 100% (always spawns), and any whole number in between that. When you think you are finished, click the "Accept" button and you're back at the full ME screen. Set your waypoints for the routing, and "Save" the scenario.
After you're set, you could open the mis file in a text editor, of which
Notepad++ is the easiest to use. You'll find your group listed as "[RndGroup X], with the "X" representing the number of it in the mis file listing. Below that "Header" is "GroupName=..." which is the name you gave the group. The reason I mention using a text file here is that you can increase the time when your group will spawn. Scroll down until you find your particular group. Then look for the two lines "DelayMin=XX" (default value is "60", for 60 minutes, or one hour). Make that value "DelayMin=1", which means that the game delays the spawn of your group for one minute. The line below that is "DelayMinInterv=XXXX" (default value for that is 1440, or 24 hours). That line is the same as the "Repeat interval" box in the Group Properties screen, but here it's in minutes, so if you so desire, set it to "DelayMinInterv=1", and then your group spawns in two minutes, instead of the 25 hours of the "default" setting of the Properties window - but it kicks a new one out every minute. You might not want that. Just remember that whatever interval you set the RGG to, is how long it will take to generate the first, such that a 60 minute DelayMinInterv for one hour, will have the RGG start spawning one hour (and one minute) after the scenario begins... One thing to remember about doing this, is that if you do further edits in the ME, it will re-set some of the text values back to their "default" values, and you're none the wiser, until the group doesn't spawn as you expect. Big thing to remember, is that your submarine cannot be inside the "spawning radius" of the group, which means at least the distance to the horizon, plus some, so I usually go for a minimum of 30 nautical miles, but prefer further, hence my mention of 40nm above.
There are disadvantages to RGG. Number one, you cannot control very easily how the group is arranged. There are a few tricks to that (their "order" in the "Define Group Contents" dialog), but for the most part, it is difficult at best to control. Also, unlike a regular Group or Unit, you cannot use the "Time" function on an RGG, and have the computer tell you when a group or unit will show up at any given place along its route, which is so nice to have with the regular groups and units. A little "trick" around that is to use a regular unit and either copy the RGG's waypoints to it (text editor), or build a similar route for it, then use the "Time" on the regular unit, and you get a rough idea on your RGG. However, regular groups or units cannot "repeat spawn". They are one-time-only generating.
For the NavalBase, which country is your submarine, and which country is the NavalBase you added? That makes a difference. Also, in order to be able to "dock" at a NavalBase, it has to be defined as a NavalBase in the Flotillas.upc file as such. Then you can transfer (or assign your boat) to it, and dock there. Also, which version of SH4 do you have? Some of the older versions (v1.3??) did not have full-functionality of certain aspects of the game...
