What do you mean by raising his forelegs? Like one at a time?
As long as the trick isn't physically demanding I have started training at 8 weeks. There is no too early for a puppy to learn (with in reason lol)
Kat is 7 months and knows touch, target, sit, down, come, is learning spin, stack, over, and how to find the weave pole entrance. Oh and she just learnt how to jump into my arms from the floor... she kinda runs up my legs.