Which of these following compounds are covalent?

All compounds have some covalent character to their bonds...

Those network compounds in which the bonds are highly polar are said to be "ionic."

It is preferable to compute the percent ionic character of a bond and to categorize them in terms of that, rather than to say either "ionic" or "covalent." The terms "ionic" and "covalent" represent the ideal bonds at either end of the bonding continuum. Real bonds have characteristics of both.

% ionic character = 100(1 - e^(-ΔEN²/4))

Aluminum hydrogensulfate ..... Al(HSO4)3 ..... covalent
Sulfur hexafluoride .................. SF6 ................ covalent
Dinitrogen pentoxide ............... N2O5 ............. covalent
Cobalt (III) carbonate .............. doesn't exist
Iron (III) phosphide .................. FeP ................ covalent
Hydrobromic Acid .................... HBr(aq) .......... H+ and Br- in soln.
Titanium (II) aceate .................. Ti(C2H3O2)2.. covalent (if it exists)
Methane ................................... CH4 ............... covalent
Copper (II) chloride .................. CuCl2.............. covalent
Silicon tetrahydride .................. SiH4 ................ covalent (aka silane)
Phosphoric acid ....................... H3PO4 ............ covalent
Nitrous acid .............................. HNO2 ..............covalent (only found in soln
Sodium dichromate dihydrate .. Na2Cr2O7•2H2O... ionic
Ammonium carbide .................. doesn't exist

Discussion.
It is highly doubtful that "aluminum hydrogen sulfate" actually exists. It does not appear in the Handbook of Chemistry and Physics or in any papers. If it did, or in the case of Al2(SO4)3 bonds between Al and O have about 57% ionic character.

In "cobalt(III) carbonate" the +3 oxidation state is too acidic to be compatible with carbonate. It will decompose to CO2.

The electronegativity values of Fe and P are so similar that the a bond in FeP would have only about 4% ionic character.

Hydrobromic acid is the solution formed when hydrogen bromide dissolves in water. Hydrogen bromide gas has bonds with 13% ionic character.

Acetate is what's left after acetic acid loses a hydrogen. If the compound exists, the metal ties two acetate radicals together to make a molecule. The bonding would have high covalent character.

Copper(II) chloride looks like it should be your typical "ionic" compound since it is a binary compound of a metal and a nonmetal. But alas, the bonds have greater covalent character and CuCl2 is merely the empirical formula for the resulting polymer.

Covalent compounds :
Sulfur hexafluoride, Dinitrogen pentaoxide, Methane, Silicon tetrahydride, Phosphoric acid, Nitrous acid, (*Hydrobromic Acid)

(* Actually, hydrobromic acid is a mixture formed by dissolving hydrogen bromide gas in water. However, hydrogen bromide is a covalent compound. Many people make confusion between hydrobromic acid (HBr(aq)) and hydrogen bromide (HBr(g)) because they have identical chemical formula but different state symbols.)

The other compounds are ionic.