Can I get forehead Botox before hairline transplantation or hairline lowering surgery?

I really don't think it makes any difference either before or after.   Glabellar and frontalis motion really have nothing to do with placement of a hairline on a 26 year old.  A hairline is a hairline.

It is best to avoid treatment with botox immediately prior to any surgery forehead or eyelid surgery so as not to adversely effect the results of surgery.  Elevation of the brows or change in appearance could mask your real issues and lead to an less than satisfactory result.

It is not a good idea as this will confuse the surgeon. Get the surgery done and let it heal completely. then if you still want Botox you can proceed