can anyone tell me why there are so much discrepancies in the orbital data of the planets of the solar system if i take those from different sources.
e.g. pluto's sidereal period from 247.7 to 248.54 years, etc..

It could be something as simple as the age of the source. As measurements get more accurate, and more information about orbital influences the numbers will change slightly.

Then there are other interpretive issues such as: is a year 365x24 or 365.2425x24 and was there any loss of accuracy due to units conversion.

__________________
Numbers are not case sensitive. (me)

The discrepancy depends on the planet you choose. Consider two authoritative sources for orbital periods:

1. Lunar & Planetary Sciences at the NSSDC
2. JPL Solar System Dynamics Group

Now look at the sidereal orbital periods (in Earth sidereal years) for the 8 planets + Pluto

The largest discrepancy is that for Pluto, a difference of ~0.24 years out of more than 247 years, or a percent difference of ~0.097%. Different sources do not all use the same astronomical databases, nor do they all use the same numerical methods to derive an orbit from the data. Those differences are easy enough to explain in terms only of those differences.

But also note another difference. The more full orbits we can observe, the better we can determine an orbit from the data. Out to Jupiter, in this table, the difference is entirely that between rounding off to 3 digits shown in the NSSDC table. Out to Jupiter we have enough precision data to observe enough orbits to get a good handle on what the orbits really are. But look at Pluto. With a period nearly 248 years, we have yet to observe one full orbit with reasonable precision, so naturally we are increasingly uncertain what it really is. So the precision & accuracy with which we can know the orbit is sensitive to the number of orbits we can observe, hence the longer the orbit, the greater the discrepancy.

And finally note that planets do not have constant orbital periods. All of these orbits are only averages over time. Each time around the sun is different for each planet because of the gravitational effects of the other planets. Those effects are not negligible, and will cause orbit changes easily detected with the level of precision given in the SSDG list. In fact, technically, the orbital period is a constantly changing variable. Compute an orbit today, and then do it again in 2 years, and you will get a different orbit for each planet.

__________________
Don't try this at home - We're what you call "professionals" - MythBusters.