DK for (I).
Whenever you have intimate relations with someone there will be an exchange of energies.
If that person has a lower vibration then it may affect you, in that you might feel tired or depleted. The more intimate relations you have will result in your integrity being compromised. This may result in not being able to Meditate so well, as your concentration is effected. You may feel not able to complete your tasks, or generally feeling strange or out of sorts.
When you are Enlightened there is a certain responsibility that comes with it, especially if you are a Teacher – be mindful of this responsibility!
The sexual act is very healthy and should be practiced regularly. However, you need to discriminate and be mindful of the consequences, especially with multiple partners.