Can I transmit an STD without penile insertion?

STD TRANSMISSION. Yes. Depending on the various std's, the phase of the disease and the virulence of the virus or bacteria, you can transmit an std during oral sex or manual contact.
Yes. Orally, anally, digitally. Depends what penile secretions (pre-ejaculate / ejaculate) come into contact with and get transferred to. Should get examined and treated.
Yes. If you have sexual contact with someone of any type, you may spread infection. Stds need only skin-to-skin contact or infected secretions-to-skin contact to spread. Practice safe sex (condoms, etc.) always and keep safe and get tested frequently!