The easiest way is probably to type the Flush Bracket number into the search on the top of the TrigTools Homepage. You will either be taken direct to a single trigpoint or given a list of possible matches.
Not really one that can be answered with this site, but probably the simplest way is to search for Guildford on a map website like www.multimap.co.uk and zoom until you can see a Ordnance Survey map, then look for some coutours.
Basically Trigpoints where classed Primary, Secondary, Tertiary or Forth Order depending on the accuracy to which they where surveyed and their intended use. (beware that currently T:UK classes Tertiary and Forth Order all as Secondary). Primary are slightly special in that they where built first and used to create a highly accurate Primary Triangulation Network covering the Whole County. The lower order trigs where then used to fill in the gaps in groups called Secondary Blocks
TrigpointingUK doesnt hold the construction dates of Trigpoints. But from OS records I think the first was built about 19/04/1935 which is probably TP2961 - Easington. Sorry if this sounds vague, but only sketchy data is available. OR if you mean the very first trigpoint logged then thats TP2757 - Delamere on the 8th Jun 1965 by JohnDarch, this is found with the When Trigpoints are logged page
The Top Ranked Trigs page is designed for just that. You can sort the results to find the best in terms of pure number of logs, how users have rated the trigpoint, the number of photos taken amonst others.
Select script 'General Statisitics' in the User section on the bottom of the TrigTools homepage, then select your username. This gives links to many of the other scripts, look for 'trigs by county' and 'view on map'
You can use this page (but as it lists every day its long!)
Select script 'When Trigs are logged' in the user section on the bottom of the TrigTools homepage. Then find the day in question on the list and click on the number of logs beside the date.
Select script 'When Trigs are logged' in the user section on the bottom of the TrigTools homepage. You can also click the number to get the list of trigs.
Use the General Statistics on the Logs section.