Hello,native English speakers. Questions about one real sentence which reflects four pairs of sentences. 1a. During this period, the new barrister will gain practical experience not to be acquired in the lecture room. 1b. During this period, the new barrister will gain practical experience not to acquire in the lecture room. Which is grammatically correct? Do they have the same meaning? 2a. During this period, the new barrister will gain practical experience which/that he can not acquire in the lecture room. 2b. During this period, the new barrister will gain practical experience which/that he can not been acquired in the lecture room. The same question as above. 3a. During this period, the new barrister will gain practical experience which he had not acquired in the lecture room. 3b. During this period, the new barrister will gain practical experience which he have not acquired in the lecture room. The same question as above. 4a. During this period, the new barrister will gain practical experience who can not acquire it in the lecture room. ( I deliberately and flexibly play grammar by use of the relative pronoun who (= the new barrister) and pronoun “it”( it = practical experience) 4b. During this period, the new barrister will gain practical experience which who can not acquire it in the lecture room. ( I deliberately and flexibly show off grammar by use of the relative pronoun which (which = practical experience) and pronoun who ( who = the new barrister) Which is/are grammatically correct? (I have never seen such a relative clause with two relative pronouns , but theoretically it works. I deem both are wrong but want to know how the native English speakers think of them.)