How many days before the wedding may a Kallah go to Mikveh?
[Lechatchila], a Kallah is to immerse in the Mikveh as close as possible to the night of the wedding. Nevertheless, the custom is that a Kallah may immerse in a Mikveh up until four nights prior to her wedding. [Thus if her wedding is on Thursday night, she may immerse starting from Sunday night.] She is not to immerse prior to this time. [However in a time of great need a Kallah may immerse even prior to four nights before the wedding.]
Doing Bedikos until the wedding night: A Kallah that immerses prior to her wedding must continue doing two daily Bedikos after her Shiva Nekiyim until she has marital relations with her Chasan after the wedding. These two daily Bedikos are required during all days in-between her seven clean days and marital relations after the wedding, and hence must be performed daily in the days between her Shiva Nekiyim and immersion [if the event that there are days in-between], and in the days between her immersion and the wedding. Thus if she completed her Shiva Nekiyiom on Sunday, went to Mikveh on Tuesday night, and is getting married Thursday night, she must continue doing two daily Bedikos until Thursday night. Furthermore, even after the wedding, if for whatever reason she did not have marital relations that first night, she must continue to do 2 Bedikos each day until she has successful intercourse. Nevertheless some Poskim are lenient in this matter once the Chupa has taken place, and hence those which are lenient to forgo these Bedikas once she has become married have upon whom to rely. In the event that the Kallah did not do any of these Bedikos past her seventh day, she nevertheless remains pure. If however seven days have passed without Bedikos prior to her Chupa [irrelevant of when she went to Mikveh], she must recount the seven days.
 Rama 192/2
 Rama ibid
 Rama ibid regarding one who immerses on Tuesday night for a Motzei Shabbos wedding, and the same applies any other time of the week, as explained in Sidrei Taharah 192
 Taharas Yisrael 192; Taharah Kehalacha 9/7
 Rama 192/2; Kitzur SHU”A 157/1 [regarding until she immerses]; Maharahm Merothenberg 320; Bach; Chochmas Adam [These Poskim apply this even after she immersed in the Mikveh, until the marital relations]; Taharah Kehalacha 9/8
The Rama ibid rules that if a woman will have five nights between her immersion and marital relations, then she must check herself daily until the Beilas Mitzvah is performed. The Poskim ibid conclude that in truth this law applies to all the days between the 7th clean day and the Beilas Mitzvah.
 The reason: As we suspect perhaps she will see “Dam Chimud”, blood of affection, until she has the first marital relations. [Taz 192/5 in name of Beis Yosef]
 Implication of Rama ibid; Lechem Vesimla 192/9; So conclude Kitzur Dinei Taharah 12/5; Darkei Taharah p. 98; Taharah Kehalacha 9/9; 12/5
 Chovos Daas 192 [brought in Piskei Dinim 192/20]
 Taharah Kehalacha 9/9 footnote 14
 Rama ibid
The reason: As the suspicion of “Dam Chimud/blood of affection” in approximation to the wedding is not as strong as the suspicion at the time of proposal to get married. [Taz 192/5]
 Sidrei Taharah; Chochmas Adam; Piskei Dinim; Taharah Kehalacha 9/10