If you have reason to be worried, go and get tested. It's too important to rely on home remedies, not all STDs will show themselves clearly anyhow. The fluid itself is perfectly natural, and doesn't indicate anything else than arousal. No need to suspect anything unless it's changed in color, smell or consistency.
Yes. That is semen. That is the only way to impregnate a woman.
why does your penis go red when you are aroused? simply because the blood is rushing to your penis
Yes, women are aroused when seeing the penis. However, this depends on how the penis looks and it depends also on how far the woman is religious and/or shy.
No
You must become sexually aroused
Pre-ejaculate.
If it is a white liquid that is excreted from the penis then it is 'the sperms.'
Girls can physiologically get an erection (their clitoris contains the same type of erectile tissue that is found in the penis) when aroused but whether they get aroused by a kiss depends on the girl. Not everyone is aroused by the same things.
When a boy penis starts shaking, it means it got aroused when you lean to it. It excites him that his penis started to moves, getting bigger, longer and harder. When you hold his penis actually, maybe, your boyfriend will release his semen untimely.
becoming sexually aroused, and a rush of blood to the penis.
It's absolutely normal--you're sexually aroused by stimulation (kissing, touching, etc.) with someone you find attractive.
You're fine. That's just called precum :)