It is 3 Ah.
No, it can't be used as a replacement of a Dewalt DC 9098 18v battery.
No, this is not compatible with a DC9099.
No, the battery is not compatible with the model #DC9098.
YES, Compatible with Dewalt DC9096, DC020, DC212, DC212B, DC212KA, DC212KB, DC212KZ, DC212N, DC213KB, DC330, DC330K, DC330KA, DC330KB, DC330N, DC380KA, DC380KB, DC380N, DC385, DC385B, DC385K, DC390, DC390B, DC390K, DC390KA, DC390KB, DC390N, DC410, DC410KA, DC410KB, DC410N, DC411B, DC411KA, DC411KL, DC490B, DC490KA, DC495B, DC495KA, DC515B, DC515K, DC515N, DC520KA, DC527, DC530KA, DC545K, DC546K, DC550, DC550B, DC550KA, DC608B, DC608K, DC616K, DC618, DC618K, DC618KA, DC628K, DC668KA, DC720KA, DC721KA, DC721KB, DC725KA, DC725KB, DC729KA, DC759 DC759KA, DC759KB, DC820B, DC820KA, DC820KB, DC821KA, DC823B, DC823KA, DC825B, DC825KA, DC825KB, DC920KA, DC925, DC925KA, DC925KB, DC925VA, DC926KA, DC926VA, DC987, DC987KA, DC987KB, DC988KA, DC988KB, DC988VA, DC989KA, DC989VA, DC998KB, DCD690KL, DCD760B, DCD775B, DCD920B2, DCD925, DCD925B2, DCD940KX.
Yes, the replacement battery can be charged with the original charger.
Yes, this is compatible.