You have to add Gmail app for that use. In that app you can add as many accounts you want. You just have to enter in your credentials.
You can install Gmail on a galaxy phone. Gmail can be installed via a Gmail app. This app can easily configure mail in that.
You can download an app on the app store or go on Safari and search "gmail" and it should come up.
You can reset the phone if it is an android. Moreover there is an option of forget password. It can reset your password if you want to.
Provided that the mobile phone has data access, you can simple go to gmail and access your emails. Depending on your phone model, you may also find a gmail app which makes emailing even easier.
You cannot remove your gmail account in android from PC. To remove it from android, you need Android only. In settings of android, you can delete it.
Samsung Phone contains the OS Android in it. You have to go to your email ID. In the ID you have the settings to change your password.
You can delete a specific Gmail address from your android. Android places the google accounts in settings. There you can delete a specific record.
Sync is an option in various Android devices. Sync can be turned off and on depending on user. If it is on, the mails would appear on time.
The clock near Gmail shows the current time. Android Phones have an application for Gmail too. The application manages the configuration of multiple accounts at a time.
The only way to find your friend's mobile number is to ask him. Unless he has posted it on his Gmail or Google-plus profile, it is not publicly available.
There is an app called "ContactsGroupU" in the Android Market . The easiest way to do this is to group your contacts in gmail on your computer. On your phone, tap on the Market icon, find and download the ContactsGroupU app, and your Droid will sync with gmail and the groups will be available on your phone through the app.
You can always reset the phone if you want. The Android system provides resetting service. It can be done by power key plus volume up.