Hello there
I will answer your questions in order where I can....
On the notes do you mean notes on a contact in the phonebook or just a general application to keep notes?
For contacts you select your contact, tap Edit, tap Add a field, tap Other and then it gives you the option of Notes.
If you just want a Notepad to use on the phone there are various ones available on the Android Market if that is available to you, I have one called Colour Note and you can either have a Text box or a Checklist.
I didn't find a place on the phone for birthdays but I use Gmail and sync my calendar and contacts on my phone with my Gmail account and online calendar. As part of that you can add a birthdays calendar for all your contacts for whom you have a birth date.
You can set different ringtones. There are a couple of options here... download an app for example Tone Picker from the market. You can use any media file, whilst playing the track in mediascape you can hit your menu button and it gives you the option to set the track as a ringtone. You can also copy tracks to your SD card in the Audio and then Notification file.
Hope this helps, if you feel that your query is answered please can you mark the thread as answered. If you need any further help please feel free to ask!!
