H1 and H4 related queries

[xyz123]

My spouse has a H4 visa. He shall be going for the H1 stamping in another three weeks. After the H1 stamping:

1. Will his H4 be still valid or will it get cancelled?
2. If his H4 remains valid then can he travel to US before 21st of September
on H4 and then travel to Mexico/Canada and re-enter US on H1?

[DMX17]

1) No. H4 should remain valid. Your spouse has to make sure that the VO does not cancel the H4.

2) Yes.