feeding depends on breed, pups activity levels etc so in general after 4 weeks + we should start roycal canine starter puppy which is more of solid food then a filler like samolac or ceralac, first introduce royal canine 30:70 ratio and then gradually increase it so by 2 months it should be ealting onlt Royal.
A medium breed would eat at least 200=250 gms per day of solid food so give it based on that proportion. The thumb rule is that the stomach of the pup should not ballon out when it eat food it should be slightly bulged.
At this age u cant healp as they are still playful and training can be started at 3 months + of age as they would gain some maturity and would understand commands. eaither dont leave u r boy outside or put a soft mouth cap.
yeah dont keep in smooth surface all day....if u can leave it on terrace for 4-6 hours to play thats fine...