I wonder if in a quantitative analysis, the absorbance measured by UV-VIS spectrophotometer should be lower than 1 Abs as I was told many years ago(Beer's&Lambert's Law) or it can be much higher up to 3 Abs because of the high tecnology of instrument in these days. If the linearity test from more than 10 concentrations of Potassium dichromate solutions(0-3 Abs) was aceptable, can I measure the high absorbance of other solutions without any verifications or validations by using that specific substances instead of Potassium dichromate.

The answer to your question is, "yes". Most newer UV-VIS spectrometers can be used for quantitative analysis even in high-absorbance situations. Their electronics are fine enough that the absorbance can be measured accurately.

It is still optimal, however, to keep the absorbance below 1.