if suppose any grp is ortho/para directing will a nucleophile or electrophile always attack the ortho/para positions. Same way if a grp is meta directing will a nucleophile or electrophile always attack meta position

Satyapraksh, See, there is nothing absolute about the reactivity or orientation of the substitution in case of organic chemistry, rather everything is relative or in respect to something, like if you talk about reactivity, then there is nothing absolute about reactivity and you can't just say that a substance X is more reactivate than Y, rather you would have to say that X is more reactive than Y in any Z properly. Similarly, the reactivity of different carbons in any system, say,  aromatic system is different with respect to type of substitution, it may be so that a carbon is electron deficient and hence favours nucleophilic substitution, whereas another carbon may be electron rich and hence favours electrophilic substitution.

Now, an ortho/para directing group increases the electron density on the aromatic ring through strong+R effect, this increase is observed more at ortho and para positions to that particular group, due to which the carbons at those positions become electron rich and hence favour electrophilic substitution whereas an electron withdrawing group does the reverse by withdrawing electron density away through-R effect and this effect decreases electron density on ortho and para positions whereas meta position doesn't have any change, so it remains richer in electron density than o- and p- positions, so it is meta- directing.

This description was in reference to electrophilic substitution reaction on aromatic ring taking into consideration the directing effect and orientation decided by the substituent group, these points get almost reversed as in case of nucleophilic substitution, as now, the carbons which has lesser electron density is favoured for substitution.

So, kindly see the type of substitution ie electrophilic or nucleophilic and then decide the effect of the group attached to the ring (whether ortho/ para- directing or meta- directing) using the points as discussed above.

Hope this helps you in your understanding of the topic.