Is there a first page/last page function in $tm1uiTable, like there is in the new Active Forms?
There is none. You can submit an RFE ticket for that.
Alternatively, you can combine the pages(), next() and previous() functions of the resulting table to get to the first and last pages.
You can set this value yourself, under the covers it is setting the index of the options object.
// First page
table.options.index = 0