I still don't understand how to perfectly use DISPLAY either. Apparently, you can only use one screen at a time... Unless you use XSCREEN 4?
Err, idk about INPUT, because I never use it. I usually GPUTCHR the question and make my own keyboard instead.
No idea, sorry. You should look at what the manual tells about it, that's what I usually do when I don't know how to use a command. (While your cursor's on the command, touch the "?" button in the up-right corner of the keyboard.)
In the program I made in PTC, I just made the game spawn 10'000 food bits, then whenever one was eaten, I would make another one spawn somewhere so there would always be 10'000 bits.
...First, remove the B=BUTTON(), it's useless. Next, remove all the GOTOs! Things like X=X+1 should go in the IF statement, and the VSYNC 1 should go in the main loop... Talking of main loop, why do you enter it with a GOSUB? Remove that thing, too.
You'll want to make your engine so all the blobs will do their things at the same time inside a FOR loop. The food bits should be managed in another FOR loop where it detects whenever a user is on a food bit, if so it removes that food bit, add 1 to the user's mass and spawn another food bit somwhere else.