No. It may mean a serious romantic relationship but you think boyfriend is inadequate. If the partner is female she is "partnerka". It can also mean business partner or dancing partner etc. But men. Only treat sb like a partner is for men and women

Yeah, it's possible. You can also use it in a heterosexual relationship to refer to your boyfriend, although that sounds... formal? And then, it can be a businesspartner or someone like that.