1. In Tosfos 2a DH u'Beis Hillel, what does tosfos mean "lo shocach ho'il"? What does this have to do with the laws of bassis?
2. On Amud bais Tosfos DH Gabei, what does tosfos mean - when do you consider it a stam v'ach'ch machlokes?
1. The phrase you quote reads 'de'Ha Lo Shachach, Ho'il ve'Hinicham Sham'.
Tosfos is referring to the Halachah that something on which a Muktzeh object is placed only becomes a Basis (and is Muktzeh) if the object was placed there on purpose, but not if it was left there inadvertently. Tosfos is therefore asking why Beis Hillel permit the removal of the table top, seeing as it is a Basis le'Davar ha'Asur, bearing in mind that he did not forget it there, since he placed it there on purpose?
2. I'm afraid I don't understand your second question. Please re-phrase it more clearly.
b'Virchas Kol Tuv,