以前 and 以来: an earlier time and a pattern since a reference
Compare a former workplace with annual visits since graduation, distinguishing a continuing pattern from uninterrupted activity.
Something at an earlier time
以前, read いぜん, can refer to an earlier time. 以前、この町で働いていました。 says that the person formerly worked in this town.
入学以前の生活を振り返りました。 says that life before enrollment was reviewed. Enrollment is the reference separating the earlier period.
A state or pattern since a reference
以来, read いらい, presents a pattern extending from a reference event. 卒業以来、毎年ここを訪れています。 says that the person has visited here each year since graduation.
日本に来て以来、毎日日本語を勉強しています。 says that the person has been studying Japanese daily since coming to Japan. Read the reference event and the recurring activity together.
Continuity and boundary wording
以前もこの店を利用しました。 says that the shop was used on an earlier occasion too. It does not also establish continued annual use afterward.
Boundary expressions using 以前 with a number or clock time may include the reference point. Unlike a general account of the past, a notice using 三時以前 calls for checking the actual cutoff conditions.
Does 卒業以来、毎年ここを訪れています。 mean staying here without a break since graduation?
Show the answer and why
No. It describes annual visits since graduation, not uninterrupted residence at that place.