1. The past tense is forbade, although forbad is occasionally used and cannot be said to be wrong. The pronunciation of forbade is -bayd or (as if it were forbad) -bad.
2. Forbid can be followed by a noun (often a verbal noun): Cars are forbidden on the beach / The law forbids smoking in public places altogether. When forbid has a personal object it is normally followed by to + infinitive: I forbid you to go / We were forbidden to go. A construction with object + from + verb in -ing is also found, on the analogy of prevent and prohibit:

• He overcame the barrier known as the ‘colour line’ which effectively forbade blacks from boxing whites —E. Cashmore, 1982

• Current laws forbid a company from operating a reactor even after it has been built —New Scientist, 1991.

Fowler (1926) regarded this construction as ‘unidiomatic’ but it has been in use since the 16c and is likely to remain so since the analogies are powerful. This construction is occasionally used with omission of from

• (The petition asked the king to forbid villeins sending their children to school —S. J. Curtis, 1948

• She'd far rather have enjoyed the company of her contemporaries and, in fact, Colonel Goreng didn't forbid her consorting with them —Timothy Mo, 1991)

but this can be regarded as non-standard. (In the 1991 example, consorting may be construed as a verbal noun qualified by possessive her).

Modern English usage. 2014.