C++ C++ issues: declaring, private -> public and setting member

[Mjmackan]

I have three errors I've researched which I do not fully understand how to solve.
Excuse me if im not providing with enough information, Im lacking bits of C++ knowledge but Im trying my best and solved most errors so far.

What I need help with is pretty much on HOW to go further solving these issues. How to declare properly, how to access or change private members to public and how to set isRewardCorpse a member of container.

Engine im using:
TFS 1.4

The code I used as base:
Reward System [remake of #1628] by cezarguimaraes · Pull Request #1641 · otland/forgottenserver (https://github.com/otland/forgottenserver/pull/1641/files)

First one is:

Error C2065 'query': undeclared identifier theforgottenserver C:\GameFatev2 -vc14\src\iologindata.cpp 452

Related to this code:

    query.str(std::string());
    query << "SELECT `pid`, `sid`, `itemtype`, `count`, `attributes` FROM `player_rewards` WHERE `player_id` = " << player->getGUID() << " ORDER BY `sid` DESC";
    if ((result = db.storeQuery(query.str()))) {
        loadItems(itemMap, result);

Secondary:

Error C2248 'Container::unlocked': cannot access private member declared in class 'Container' theforgottenserver C:\GameFatev2 -vc14\src\reward.cpp 10

Related to this code:

#include "otpch.h"

#include <iostream>
#include "reward.h"

Reward::Reward() :
    Container(ITEM_REWARD_CONTAINER)
{
    maxSize = 32;
    unlocked = false;
    pagination = true;
}

Third one:

Error C2039 'isRewardCorpse': is not a member of 'Container' theforgottenserver C:\GameFatev2 -vc14\src\actions.cpp 401

Le code:

        uint32_t corpseOwner = container->getCorpseOwner();
        if (container->isRewardCorpse()) {
            //only players who participated in the fight can open the corpse
            if (!player->getReward(container->getIntAttr(ITEM_ATTRIBUTE_DATE), false)) {
                return RETURNVALUE_YOUARENOTTHEOWNER;
            }          
        } else if (corpseOwner != 0 && !player->canOpenCorpse(corpseOwner)) {
            return RETURNVALUE_YOUARENOTTHEOWNER;
        }