Let's take them one by one.
1. You can do <n>,$y in the command mode where n is the number of line and $ represents end of file. e.g. :15,$y
2. you can just enter the line number in command mode. e.g. :20 with place the cursor at line 20.
3. You can always do a set nu in command mode and check it.
4. Do a !<command name> in escape mode.
5. Can you eloborate more on what you want.
I am also a novice ....but i think this might be helpful
regards
Apoorva Kumar