1. you can use automation to change the bpm in your song. try looking up a tutorial on automation and just mess around w/ it for a while
2. i'd recommend ample guitar lite for a start, but again just do some research on youtube and you'll find plenty of other free options
3. yep
4. updates will be released and you'll just have to download them manually i believe. i'm still on lmms 1.2.2 right now lmao
5. not much we can do if we can't code, but i guess the best thing you can do is tell your friends about it and stay in the community

happy producing!