What is the ruling on lying and claiming that seclusion with the suitor did not occur in order to avoid the rulings of divorce after seclusion? And do the rulings of divorce after seclusion differ from those before it? And is concealing seclusion considered a sin?

The issue can be summarized as follows: If a husband divorces his wife before consummation or a valid seclusion (khalwah sahihah), she becomes irrevocably divorced (ba'inat) from him, and he does not have the right to take her back (raj'ah) except with a new contract. However, if he divorces her after a valid seclusion in which sexual intercourse is usually possible, the opinions of the jurists (fuqaha) differ:

Some of them (the Hanbalis) hold that it has the ruling of consummation, and the husband retains the right of raj'ah during the 'iddah (waiting period).

Others (the Hanafis) believe that raj'ah is permissible if the husband admits to sexual intercourse, but he has no right of raj'ah if he denies intercourse.

As for the Malikis, they hold that raj'ah is only established if both spouses admit to sexual intercourse.

If a husband secludes himself with his wife in a valid seclusion after the marriage contract, this should not be concealed due to the rights that stem from it, unless the husband consents to concealing the matter.