For Q1: I believe "Cash-in to Self" means depositing money to your own GCash account. This is similar to depositing money to your bank account. Thus, there's no charge for that transaction.
Q2: "Send Money at an Outlet" means transferring money to a GCash partner outlet. For example, you want to send money to your relatives in the province and they don't have GCash, what you need to do is send GCash fund to a partner outlet. Your relatives will then proceed in claiming these funds at that outlet. This is similar to money transfer service.
"Cash Out", on the other hand, means withdrawing your money from your GCash account.
Q3: Charge is P20 in multiples of 1000. Also, charges may vary as well depending on the GCash outlet. With Globe Business Centers, they follow this scheme.
Check the link below to know more about GCash: