Is retin-a micro safe as an acne medicine?

See below: Generally, yes, assuming you're not pregnant and take proper precautions regarding sunlight exposure. In addition, it's always important to read the package insert.

Yes: ...But it will make you sun-sensitive. Use it as directed, usually at night-time, after washing your face and drying thoroughly. Micronized version is usually better tolerated. Start with the lowest strength.