Could this activity be carried out with spotting tiles instead of test tubes?

Yes, the activity can be adapted to use spotting tiles or laminated sheets where they could be wiped clean and re-used another time. You could print your own large versions of the tables in the student worksheets that allow sufficient space for a small 'puddle' of buffer solution and indicators to be dropped onto this sheet when it has been laminated.

Is our laboratory Universal indicator made up of these four indicators? And why is Universal indicator sometimes called, 'full range indicator'?

A universal indicator is the term for any indicator giving gradations in pH, normally from pH3 to about pH12. Full range indicator similarly has gradations in pH and it is wider in its range, from aout pH1 up to pH14